Plastering walls may involve either the application of a textured surface to the plastered wall, often referred to as float work, or forming a smooth wall surface without marks or texturing of any type, often referred to as finish work. Heretofore, tools have been especially designed for float work, but few have been especially designed for finish work. Float work tools or floats heretofore designed frequently provide specially formed blades to assist in creating a textured surface, while conventional finish work trowels are formed with flat rectangular rigid steel blades. There are also other differences between float and finish trowels.
In float work, the texturing applied to the surface of the plastered wall is achieved by rotating the trowel in a circular movement. The trowel is generally held flat against the wall and is moved in a circular motion. Trowels that are normally used for this float work are optimally designed with handles secured to the trowel blade at both ends. Such float trowels are not designed or intended for use on finished work.
Finished work trowels, on the other hand, are designed with handles which are secured only at one end to the base plate of the trowel. By securing the handle only at one end, the trowel may be rotated more readily about an axis parallel to the handle in a feathering motion during plastering. In finished work, unlike the float work, the flat portion of the trowel is not always held against the wall but is rotated away from it at the end of the stroke to achieve a feathered edge and to blend the end of the section of plaster being applied to adjacent portions of plaster.
Because of the motion by which finish work is achieved, the metal, non-resilient edges of conventional finish work trowels are not ideally suited for such finish work. Limitations on trowels heretofore available for finish work has been accented by further developments in plastering materials which are now currently in common use. Previously a rock lathe with a base gypsum coat was first formed when making a plastered wall. As a rule, several days later a lime finish coat was applied. When a lime finish coat was used, moisture would be readily sucked into the previously dried gypsum coat. The quick drying of the lime coat permitted a quick set with little feathering problems, since the finished coat of plaster became hard quite quickly. For that reason, there was no serious need for the plasterer to feather the edge of the stroke with any great care. More recently, plaster walls are formed using a one-coat system in which a single layer of plaster is applied over a base layer or blue board. The single layer of plaster is applied while still quite wet. Unless the plasterer is quite careful, a mark is left at the end of each trowel motion. This requires great skill and care by the plasterer. It further requires a careful feathering motion.